The present invention relates to a compression system, a multicylinder rotary compressor constituting the system, and a refrigeration apparatus using the compressor.
This type of compression system has heretofore comprised a multicylinder rotary compressor, a control device which controls an operation of the multicylinder rotary compressor and the like. Examples of this multicylinder rotary compressor includes a two-cylinder rotary compressor comprising first and second rotary compression elements. The compressor includes a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, and these elements are housed in a sealed container. The first and second rotary compression elements comprise: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders, respectively; and first and second vanes which abut on the first and second cylinders to partition the insides of the respective cylinders into low-pressure and high-pressure chamber sides. The first and second vanes are constantly urged toward the first and second rollers by the spring members.
Moreover, when the driving element is driven by the control device, a low-pressure refrigerant gas is sucked from a suction passage on the low-pressure chamber sides of the respective cylinders of the first and second rotary compression elements. The gas is compressed by operations of each roller and vane to constitute a high-temperature/pressure refrigerant gas, and discharged from the high-pressure chamber side of each cylinder to a discharge muffling chamber via a discharge port. Thereafter, the gas is discharged into the sealed container, and discharged to the outside (see, e.g., Japanese Patent Application Laid-Open No. 5-99172).
In the compression system comprising this multicylinder rotary compressor, in a case where a compression operation is performed by both the first and second cylinders in a small capacity region at a light load time or a low-speed rotation time, the refrigerant gas has to be sucked and compressed for displacement volumes of both the cylinders. Therefore, a rotation number of the driving element is lowered by a corresponding number by the control device to operate the element. However, when the rotation number drops excessively, a problem occurs that efficiency of the driving element drops and leak loss increases to lower the operation efficiency remarkably.
Therefore, in view of this problem, a compression system has been developed in which a one-cylinder operation and a two-cylinder operation are switchable in accordance with the capacity. That is, either spring member is eliminated from the spring members which urge the first and second vanes of the multicylinder rotary compressor toward the first and second rollers. For example, the spring member is eliminated which urges the second vane toward the second roller. A refrigerant pressure is applied as a back pressure of the second vane on discharge sides of both the rotary compression elements by the control device at the two-cylinder operation. Accordingly, the second vane is urged on a second-roller side to perform a compression work.
On the other hand, when the two-cylinder operation is switched to the one-cylinder operation, a refrigerant pressure is applied as the back pressure of the second vane on suction sides of both the rotary compression elements by the control device. Since this suction pressure is a low pressure, the second vane cannot be urged on the second-roller side. Therefore, the compression work is not substantially performed by the second rotary compression element, and the compression work of the refrigerant is performed only by the first rotary compression element.
When the one-cylinder operation is performed in a small capacity region in this manner, an amount of the refrigerant gas to be compressed can be reduced, and the rotation number can be raised by the amount. Consequently, the operation efficiency of the driving element is improved, and the leak loss can be reduced.
Here, in the second rotary compression element in which any spring member is not disposed during the two-cylinder operation as described above, as to the discharge-side pressures of both the rotary compression elements which urge the second roller, pressure fluctuations are large, a follow-up property of the vane is deteriorated by the pressure fluctuation, and a collision sound is generated between the second roller and the second vane. Therefore, the applicant has tried the application of an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements as the back pressure of the second roller.
However, when the above-described intermediate pressure is applied as the back pressure of the second vane, and the one-cylinder operation is switched to the two-cylinder operation, much time is required for allowing the second vane to follow up the second roller, the second vane collides with the second roller during the follow-up, and a disadvantage has occurred that a collision sound is generated.
On the other hand, since equal suction-side pressures are applied to the pressure in a second cylinder and the back pressure of the second vane at the time of the one-cylinder operation, the second vane does not easily retreat from the second cylinder during the switching from the two-cylinder operation to the one-cylinder operation. There has a problem that the second vane collides with the second roller and the collision sound is generated even during the switching.
On the other hand, pressure pulsation is caused on the back-pressure side of the vane (side opposite to the roller) by the urging operation of the vane with respect to the roller at the time of the operation of the multicylinder rotary compressor. However, in the second vane in which any spring member is not disposed, the pressure pulsation causes a problem that the follow-up property of the second vane is deteriorated, the vane collides with the second roller, and the collision sound is generated.
Furthermore, as to the discharge-side pressures of both the rotary compression elements, which are applied as the back pressure of the second vane, the pressure fluctuation is large, accordingly the follow-up property is deteriorated in the second vane in which any spring member is not disposed, and the collision sound is generated between the second roller and the second vane.
Moreover, the second roller is brought into an idling state in the second rotary compression element during the one-cylinder operation. At this time, the equal suction-side pressures are applied to the pressure in the second cylinder and the back pressure of the second vane. Therefore, the second vane protrudes into the second cylinder by the function of the balance between both spaces. Even in this case, there has been a problem that the second vane collides with the second roller, and the collision sound is generated.